As all Center components will use genetically engineered mice, a central Animal Breeding Core (AB Core) will be used to meet the animal needs of all Center projects. The AB-Core was established in the previous funding cycle and developed a set of standardized procedures to accomplish this goal. The aims of the AB-Core are as follows: 1. The AB-Core will co-ordinate with each component to provide the required cohorts of mice as needed. 2. The AB-Core will maintain each line under optimal breeding management practices. 3. As many components will utilize cross-bred lines, the AB-Core will ensure all lines are correctly maintained as congenic on the C57BL/6J background. 4. The AB-Core will follow the correct breeding strategies to ensure wild type and mutant mice are bred as littermates. 5. The AB-Core will verify that correct patterns of expression are achieved following cre- mediated deletion in both males and females.